应用肝分区评估法对不同铅门模式门脉癌栓螺旋断层放疗剂量学特性分析

目的:应用肝脏分区评估的方法探究不同铅门模式下门脉癌栓螺旋断层放射治疗的剂量学特性。方法:选取12例门脉癌栓患者,根据靶区与肝脏解剖关系将肝脏超出靶区上缘部分定义为肝上区（Lsup）,超出靶区下缘部分定义为肝下区（Linf）,中间部分定义为肝中区（Lmid）。分别设计射野宽度（FW）为1.0、2.5、5.0 cm 3组静态铅门（FJ）计划（F1.0、F2.5、F5.0）及FW为2.5、5.0 cm 2组动态铅门（DJ）计划（D2.5、D5.0）。分析比较各计划组靶区、各危及器官剂量学差异并评估各计划实施效率。结果:5组计划得到近乎相当的靶区剂量分布。在相同FW情况下,DJ能显著降低全肝受照剂量,并且可以达到与比之小一档FW静态计划近乎相当的水平。而FW同为2.5、5.0 cm两种情况下,DJ计划较FJ计划的Lsup平均剂量分别降低35.5%、51.3%,而Lmid平均剂量变化较小。在各铅门模式下,随着FW的增加Lsup受照剂量显著增加,而Lmid受照剂量虽表现出略有增加的趋势,但无统计学意义。计划实施时间随FW增大而明显增加,相同FW下DJ计划机架旋转周期及计划实施时间均有一定程度的增加。结论:DJ技术可有效降低由于FW增加而引起的靶区纵向边缘剂量延伸,进而提高靶区纵向边缘的剂量梯度,可在纵轴方向上对肝脏等危及器官和正常组织的受照剂量起到显著的降低作用。

Liver segment-based assessment of dosimetric characteristics of helical tomotherapy for portal vein tumor thrombus under different jaw modes

Abstract: Objective To explore the dosimetric characteristics of helical tomotherapy for portal vein tumor thrombus under different jaw modes by liver segment-based assessment. Methods Twelve patients with portal vein tumor thrombus were enrolled in the study. According to the anatomical relationship between the target area and the liver, the liver was divided into 3 parts, namely Lsup which was defined by the part beyond the superior edge of the target area, Linf which was defined by the part beyond the inferior edge of the target area, and Lmid which was defined by the middle part. Three groups of fixed jaw (FJ) plans with the field width (FW) of 1.0, 2.5 and 5.0 cm, respectively, were designed and defined as F1.0, F2.5 and F5.0 and two groups of dynamic jaw (DJ) plans with FW of 2.5 and 5.0 cm were designed and defined as D2.5 and D5.0. The dosimetric differences of the target area and organs-at-risk were analyzed and compared among different groups, and the delivery efficiency was also evaluated. Results The dose distributions in the target area were similar in 5 groups. With the same FW, DJ plans reduced the irradiation dose of the whole liver significantly and obtained the result that was close to that of FJ plans with smaller FW. When FW were 2.5 and 5.0 cm, the mean dose of Lsup in DJ plans was decreased by 35.5% and 51.3% as compared with that of FJ plans, but the mean dose of Lmid varied slightly. The irradiation dose of Lsup increased obviously with the increase of FW under each jaw mode, while the irradiation dose of Lmid showed a trend of slight increase, and there were no statistical significance. The delivery time was increased significantly with the increase of FW. With the same FW, the gantry periods and delivery time of DJ plans were increased. Conclusion DJ technique can be used to not only effectively reduce the dose extension along the longitudinal edge of the target area due to the increase of FW, thereby increasing the corresponding dose gradient, but also significantly decrease the irradiation doses of normal tissues and organs-at-risk such as liver.